Dell XPS 16 9640 USB or Thunderbolt device is not recognized

The checks in more detail

Each uses a different part of the port, so a problem with one does not mean the port has failed. Test each piece separately. Try the device in each port and on another computer, with another cable; a high-speed drive may need a Thunderbolt or USB 3.2 cable, and a cheap cable gives slow transfers or dropouts. A camera or a card reader may need a data cable, and an audio interface may draw a lot of power, so test it with its own supply.

For an external display or a dock, check the cable and the adapter and test it with another laptop. A slow drive on a slow cable is the commonest cause of a transfer that seems stuck. Then the computer. Restart with accessories out and add them one by one. In Device Manager, look under Universal Serial Bus controllers and Thunderbolt for a warning symbol, uninstall the device and restart. Update the BIOS, the Thunderbolt controller and the chipset drivers through Dell SupportAssist, since firmware updates fix many port problems; also update any dock's firmware.

Make sure the laptop is using a charger with enough wattage, because a weak charger with several devices can cause ports to drop out. Check Windows power settings, particularly USB selective suspend. If a port fails with every device and cable, power-cycle it: shut down, unplug everything, hold the power button for 20 seconds and restart. A port that is loose, bent or dead is a hardware fault; Dell's service can repair it under warranty. Quote the service tag from the underside.